Electron discharge device



R. W. SEARS ELECTRON DISCHARGE DEVICE Filed May 2 1945 PULJE INPUT 6+ FIG. 3.

BEAM DEFLECTION FOR I POSITIVE PULSE-f TO 24 35 F0)? NEGATIVE PULSE To I BEAM Pas/won Fan N0 DEFLECT/Ol'l 5214,25

85AM DEFECT/Dal 2 Sheets-Sheet 1 INVENTOR By RW SEA RS ATTORNEY mmw R. W. SEARS ELECTRON DISCHARGE DEVICE Filed May 2, 1945 2 Sheets-Sheet 2 FIGS m H m a//%/%////,///// M M, l

E m all m m mm PULSE INPUT AA VV nan scr/a/v ran m1 Til E PULSES DEFLECTION M mm was r/ve PULSE-f To me:

POSITION FDRNO 0 DEFLECTING PULSE INVENfOR 8y RWSEARS Wm GM Patented Mar 18, 1947 ELECTRON DISCHARGE DEVICE Raymond W. Sears, WestOrange, to Bell Telephone Laboratories, New York, N. Y., a. corporation of N. J., assignor Incorporated, New York Application May 2, 1945, Serial No. 591,505

20 Clai\ms. (Cl. 315-21) This invention relates to electron discharge devices and more particularly to such devices of the multi-anode beam type.

One general object of this invention is to improve multi-anode electron beam discharge devices and particularly such devices especially suitable for switching and signaling purposes.

More specifically, objects of this invention are to:

Simplify electronic switching apparatus;

Increase the operating flexibility of multianode electron beam discharge devices whereby a single device is capable of operation in a variety of manners to perform a multiplicity of functions;

Enable the selective transfer of the electron beam in a multi-anode electron discharge device from one anode to another or to a series of anodes in a prescribed sequence;

Realize automatic locking of the beam in such devices in a desired position to which it has been deflected. upon cessation of the condition or signal resulting in the deflection;

Achieve automatic resetting of the electron beam in such devices to a desired position after it has been deflected to another desired position or to a sequence of positions; and

Increase the frequency of switching attainable in electron beam discharge devices of the multianode type.

In one illustrative embodiment of this invention, an electron discharge devicecomprises a plurality of anodes or target electrodes mounted in a line, an electron gun for projecting a concentrated electron beam toward the anodes or target electrodes, a pair of deflector plates arranged to effect deflection of the electron beam in the direction of alignment of the anodes or target electrodes, and a second pair of deflector plates arranged to efiect deflection of the beam in a dimension at an angle, e. g., a right angle, to the direction noted.

In accordance with one feature of this invention, means are provided for causing deflection of the electron beam in the direction noted when a signal voltage or pulse is applied to the second pair of deflector plates.

In accordance with a more specific feature of this invention, an auxiliary electrode is provided, for example between the deflector plates and the anodes or target electrodes, and is associated with the first deflector plates in such manner that when the beam is deflected by a signal voltage or pulse applied to the second deflector plates, a deflecting voltage of preassigned amplitude is cstablished between the first pair of deflector plates.

In accordance with another feature of this invention, the deflector plates and auxiliary electrode are so constructed and arranged that initially the beam impinges upon a preassigned anode or target electrode and upon application of a series of pulses to the second deflector plates the beam is stepped from one anode or target electrode to the next adjacent one, one step per pulse, and remains upon any anode or target electrode to which it is stepped until the next succeeding pulse.

In accordance with a further feature of this invention, the auxiliary electrode is constructed so that upon the application of a pulse of certain polarity and amplitude to the second pair of deflector plates, the beam is reset to a preassigned position.

In accordance with still another feature of this invention, the deflector plates and auxiliary electrode are cooperatively designed and associated so that the beam may be stepped from one target electrode or anode to either the next preceding or the next succeeding one by application of a pulse of appropriate polarity to the second pair of deflector plates.

In accordance with a still further feature of this invention, a second auxiliary electrode is provided in association with the first auxiliary electrode for automatically transferring the beam to one of the end anodes or target electrodes whenever it is deflected beyond the other end anode or target electrode.

The invention and the above-noted and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which:

Fig. 1 is a diagram of an electron discharge device and associated circuit illustrating certain principles involved in apparatus constructed in accordance with this invention;

Fig. 2 is in part a perspective view of an electron discharge device and in part a circuit diagram showin an illustrative embodiment of this invention;

Fig. 3 is an enlarged face view of the auxiliary electrode included in the device shown in Fig. 2, several positions of the electron beam being indicated thereon;

Fig. 4 is a. view, similar to Fig. 3, illustrating the construction of another auxiliary electrode which may be incorporated in a device of the construction shown in Fig. 2;

Fig. 5 is a perspective view and diagram similar to Fig. 2 illustrating another embodiment of this invention; and

Fig. 6 is a fragmentary perspective view showin details of the auxiliary electrodes included in the device illustrated in Fig. 5.

Referring now to the drawing, the electron discharge device illustrated in Fig. 1 comprises an evacuated enclosing vessel I having mounted therein, at one end, an electron emitter, such as an electron gun or thermionic cathode ll, opposite and in alignment with which there is positioned a cylindrical aczelerating anode l2 which functions to focus the electrons emanating from the cathode into a concentrated stream projected toward the opposite end of the enclosing vessel.

Also mounted within the vessel H) are a target electrode I3 and an auxiliary or beam guiding electrode l4, Positioned between the auxiliary electrode l4 and the cathode II are parallel deflector plates [5 and I6 and a second focussing electrode H, which may be defined by a conductive coating upon ithe inner wall of the enclosing vessel l0.

The electrodes l2 and H are operated at a positive potential relative to the cathode H and together with the deflector plate l5 may be connected to ground as shown. The other deflector plate I5 together with the auxiliary electrode M are connected to ground by way of a resistor iii. The target electrode I3 is connected to ground by way of a load indicated as a resistor l9.

When potentials are applied initially to the electrodes of the device, the electron beam will be directed upon the auxiliary electrode It, the beam path being substantially as indicated by the broken line a in Fig. 1. As a result of the electron flow thereto, the auxiliary electrode becomes charged. If the secondary electron emissive ratio of this electrode is less than unity, the charge thereon is negative. The deflector plate l5, being tied to the electrode l4, likewise becomes charged negative so that the beam is deflected, downwardly in the device shown in Fig. 1, to a position such as indicated by the broken line b and impinges upon the target electrode l3. If the beam passes beyond the lower edge of the electrode M, the charge upon the plate I5 is dissipated at a rate determined by the time constant of the resistor-capacitive circuit constituted by the resistor l8, the condenser defined by the deflector plates l5 and i6, and the capacitance between the plate l5 and ground. As the condenser discharges, the negative potential upon the plate l5 decreases and, as a result, the beam moves upwardly until it again impinges upon the electrode I4. Quickly an equilibrium condition will be reached at which the beam is at such position that the charge upon the deflector plate I5 is just sufficient to hold the beam fixed. This condition is reached when the beam just grazes the lower edge of the electrode [4, supplying sufficient current to this electrode to maintain the deflector plate l5 at the potential requisite to effect deflection of the beam to this position. Advantageously the resistance I8 is made large so that this current is small, The major portion of the beam current flows to the target electrode l3.

If, now, a potential is impressed between the deflector plates l5 and I6, as by the application of a signal pulse in circuit with the resistor i8, the stream will be deflected in one direction or the other, that is upwardly or downwardly in Fig. 1, depending upon the polarity of this potential. Upon the cessation of the pulse, the beam will be shifted automatically to the position corupon the electrode 14 by a small beam current.

If there were a series of "electrodes l3 and 14 mounted in line parallel to the direction of beam deflection, it will be appreciated that there would be a plurality of beam positions, one for each target, for which an equilibrium condition would exist. Thus, the beam could be shifted from one target to another by application of a'suitable signal pulse effective to cause deflection of the beam, and at the cessation of the pulse would continue to impinge upon the target electrode to which it was shifted.

Apparatus, illustrative of one embodiment of this invention, for realizing this and other results is shown in Fig. 2. The electron discharge device illustrated in this flgure is similar to that shown in Fig. 1 but is provided with a plurality of target electrodes l3a to l3e inclusive, each having a respective load l9, indicated as a resistor, connected thereto. The auxiliary electrode comprises two similar parts MA and MB each having, as shown clearly in Fig. 3, a side or base portion 20A or 203 and a plurality of parallel finger portions MA or 2|B respectively, the fingers of the two parts being in equally spaced interleaved and partially overlapping relation. The auxiliary electrode is of a material, such as a silver-magnesium alloy, having a secondary emission ratio greater than unity and the two parts thereof are connected together and to the deflector plate l6 which in turn is connected to ground by way of the resistor l8. Secondary electrons emanating from the auxiliary electrode MA, MB are collected by the electrode H, which is maintained at a positive potential by a source such as a battery 22.

A fixed potential, of preassigned amplitude noted hereinafter, is applied between the deflector plates [5 and I6 by a source such as a battery 23.

Disposed between the auxiliary electrode MA, MB and the deflector plates l5 and i6 and at right angles to the latter are parallel deflector plates 24 and 25 which are connected across an input resistor 26, the mid-point of which is grounded as shown.

The auxiliary electrode and deflector plates 24 and 25 are constructed and arranged in such relation that, as indicated in Fig. 3, for no potential difference or a preassigned initial difference between the plates 24 and 25, the beam is at a point on the line 0-0, for an input pulse of preassigned amplitude and one polarity it will move to a point on the line X--X passing through the side or base 20A of the electrode part MA, and for a pulse of this amplitude and the opposite polarity, it will shift to a point on the line Y-Y. The potential applied between the deflector plates l5 and I6 by the source 23 is made of such amplitude and polarity that initially the beam impinges upon or .just grazes the uppermost flnger 2IA in Fig. 3, of the electrode part MA and impinges upon the target electrode In, as indicated by the point a and broken line a respectively in Figs. 3 and 2, so that the beam is in an equilibrium position. The beam current to the electrode part MA is but a small fraction of the total beam current, the remainder flowing to the target electrode I3a.

When a signal puls is applied across the input resistor 26, the beam will be deflected laterally in the direction determined by the polarity of the pulse. For purposes of discussion, it may be assumed that for a negative input pulse, the beam will be deflected to the left in Fig. 3 and will deflect to the right for a positive pulse, and that the pulse amplitude is such as to result in deflection to a position corresponding to either the line X-X or Y-Y. Now, when, in response to a negative-pulse, the beam is deflected to the left from position a so that it impinges upon the side or base portion 20A, the auxiliary electrode part MA will become positively charged, inasmuch as the auxiliary electrode material has a secondary emission ratio greater than unity. Consequently, the deflector electrode l 6 will have a positive voltage component applied thereto and the beam will travel along the side or base 20A to an equilibrium position indicated at f, i. e., in grazing incidence with the electrode part MA. Upon the cessation of the input pulse, the beam deflects, to the right in Fig. 3, to the equilibrium position indicated by e and remains in this position, so that the greater portion of the beam current flows to the target electrode I3e.

If, now, a positive pulse is applied to the input resistor 26, the beam will be deflected to the right in Fig. 3 to a point beyond the end of the lowermost finger 2|A of the electrode part MA. As a result, the charge previously placed upon the deflector plate 16 is dissipated at a rate dependent upon the time constant of the circuit constituted by the resistance I8, condenser defined by the deflector plates l5 and It, the capacitance between the plate I6 and ground and the source 23, and the beam moves upwardly to the equilibrium position indicated by e in Fig. 3. When the input pulse ceases, the beam moves to the left beyond the lowermost finger 2|B of the electrode part NB, the charge on the plate l6 decreases still further and the beam comes to rest at the equilibrium position indicated by d, with the major portion of the beam current flowing to the target electrode l3d.

For each succeeding positive input pulse applied to the input resistor 26, the beam will be shifted to the next higher equilibrium position, i. e., c and then b, and, thus, is stepped from one target electrode l3 to the next adjacent one, e. g. from electrode id to electrode l3c, from the latter to electrode l3b, etc. Thus, the electron beam may be shifted from its initial position indicated at a to impinge upon the target electrode |3e and thereafter to impinge upon any other target electrode by the application of a pulse or series of pulses to the input resistor 26 whereby any one of the loads l9 may be energized or several of such loads may be energized in sequence.

If the beam has been shifted or stepped to any one of the positions indicated by a, b, c or d,it can be returned or reset to the position e by the application of a, negative pulse to the input resistor 26 sufficient to cause the beam to impinge upon the side or base portion 20A of the electrode part MA, inasmuch as, when the beam impinges upon the portion 20A, the deflector plate I 6 is charged to the potential requisite to deflect the seam to the position indicated at f. Also, as is apparent, the beam may be reset to the position indicated at d from any of the positions indicated at a, b and c by the application of a positive pulse to the input resistor 26, of appropriate duration and of amplitude sufllcient to cause the beam to fall upon the side or base portion 203 of the electrode part MB.

Thus, the beam may he stepped in either direction, that is upwardly or downwardly in Fig. 3, to impinge upon the target electrodes l3 in any desired sequence, and, hence, to close the load circuits associated with these electrodes in like sequence, by application of pulses of appropriate amplitude and polarity to the input resistor 26.

Of course, in any particular device, certain relationships of parameters should be observed. The beam should be highly concentrated and the space between adjacent fingers HA and ZIB must be greater than the diameter of the beam. The stepping voltage pulse, i. e., the positive stepping pulse in the case described above, must be sufliciently great to deflect the beam from a point on the line O-O to beyond the ends of the fingers ZIA but less than the value requisite to cause the beam to strike the side or base portion 208. Also, the stepping pulse must be of sufiicient duration to allow dissipation of the charge upon the plate l6 through the resistor [8 so that the charge can decrease from a value corresponding to one beam position such as e to a value corresponding to a next succeeding beam position such as e. As noted heretofore, the rate of dissipation of the charge is determined by the time constant of the resistive-capacitive combination I8 and [5, I6. The reset pulse must be of amplitude just sufficient to deflect the beam from a position on the line O-O to the side or base portion 20A or 203 and must be of sufficient duration, at the maximum, to allow charging of the deflector plate l6 from its initial value to the value corresponding to beam position f.

The stepping frequency will be determined primarily by the capacitance of the condenser defined by the plates l5 and [6, the resistance l8, the secondary emission ratio of the auxiliary electrode M, the total beam current and the fraction of the total beam current which is taken by the auxiliary electrode Id when the beam is at an equilibrium position, e. g., at e. For example, in an illustrative device, stepping frequencies of the order of 10 kilocycles per second, corresponding to a stepping pulse length of about 0.1 millisecond, may be realized for the following parameters:

Capacitance of condenser l5, l6

Hence, extremely rapid stepping of the beam or, viewed in another way, switching from one load circuit to another, can be attained.

In a modification of the apparatus shown in Figs. 2 and 3 and described hereinabove, the auxiliary electrode I 4A, [4B is constructed as illustrated in Fig. 4. The part MA of this electrode is provided with parallel slanting portions 21 extending between successive fingers 2|A. When the beam is deflected from its initial position, indicated at a, by an increasing signal pulse applied to the input resistor 26, it moves toward the slanting portion 21 extending between the two beam from the position 7 uppermost fingers 2IA. When it reaches this position, the deflector plate l6 receives a charge which tends to deflect the beam downwardly. Under the influence of the deflectingforce due to this charge and the deflecting force due to the signal pulse, the beam passes successively to a series of positions such as indicated at m, a: and as, the latter corresponding to substantially the maximum value of the stepping pulse. As this pulse then decreases, the beam is deflected to the right to the position indicated at a4 and then to the equilibrium or zero pulse position indicated at b and will impinge upon the target electrode 13b. Succeeding pulses of polarity to de- I flect the beam to the leftin Fig. 4 will step the indicated at b to that indicated at c, then to the position indicated at d, and so on. If, while the beam is at any of the positions indicated at b to e a pulse of the opposite polarity is applied to the input resistor 26, the pulse being of amplitude to deflect the beam to the right, in Fig. 4, beyond the ends of the fingers 2IA, the beam will be stepped to the next preceding equilibrium position in the manner described heretofore in the discussion of the device shown in Figs. 2 and 3. Thus, by 'appropriate selection of the polarity of the stepping pulse, the beam may be switched from one target electrode Hi to either the next succeeding or next preceding target electrode. Hence, the beam may be stepped in either direction, up or down in Fig. 4, and brought to rest upon any desired target electrode or upon several target electrodes in any desired sequence.

By application of a signal pulse sufficient to deflectthe beam to the side or base 20A, with consequent charging of the deflector plate IS, the beam may be reset from any target to a desired position. For example, by appropriate correlation of the parameters, the beam may be reset in this manner to the position indicated at c in Fig. 4.

For some applications of the apparatus illustrated in Figs. 2 and 3 and described hereinabove, it i desirable that the beam be reset automatically to the position indicated at e whenever it reaches the position indicated at a. This may be effected by modifying the apparatus of Figs. 2 and 3 in the manner illustrated in Figs. 5 and 6. Specifically, a reset electrode is provided between the uppermost finger 2|A and 2IB and electrically separate from the auxiliary electrode MA, NB, the reset electrode having a portion 28 parallel to and slightly below the uppermost finger HA and a portion 29 partially overlapping and spaced from the face of the side or base portion 7 20A toward the deflector plates. The reset electrode 28, 29 is connected to the deflector plate 24.

Whenever the electron beam is stepped to the position indicated at a in Figs. 2 and 6, a portion of the beam current is intercepted by the reset electrode and as a result it becomes charged positive and a positive charge is placed upon the deflector plate 24. Consequently, the beam is deflected along the reset electrode to the position indicated at a in Fig. 6. Upon reaching this position, a portion of the beam current flows to the side or base portion 20A so that a charge is placed upon the deflector plate 16 and, as a result, the beam is deflected to the position indicated at e in Fig. 2. Of course, when the beam leaves the reset electrode 28, 29, the charge upon the deflector plate 24 is dissipated, specifically through the left-hand portion of the resistor 26 in Fig. 5, so that when the beam reaches position e the deflector plates 24 and 25 are at the same potential.

It will be appreciated that this invention provides electronic devices capable of effecting energization of a plurality of load circuits selectively as, for example, in a desired sequence. The switching from one circuit to* another is accomplished by signal pulses so that little expenditure of power is entailed and high operating efllciencies are attainable. Further, it is apparent that relatively simple circuits may be utilized to provide the requisite signal pulses and that auxiliary equipment, necessary to effect stepping oi the beam from one target to another is minimized. Moreover, as has been pointed out heretofore, high frequency switching can be attained.

Although specific embodiments of the invention have been shown and described, it will be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An electron discharge device comprising a plurality of targets mounted in a row, means for projecting an electron beam toward said targets, and means for selectively directing said beam to impinge upon one or another of said targets, said directing means comprising a first deflecting means effective when energized to deflect said beam in the dimension parallel to said row, a second deflecting means effective when energized to deflect said beam in a direction at an angle to said dimension, means for energizing said second deflecting means and means responsive to deflection of said beam by said second deflecting means for energizing said first deflecting means,

2. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, and means for stepping said beam from one target electrode to another, said stepping means comprising deflector plate means for deflecting said beam in the direction parallel to said row, deflecting means for deflecting said beam in the direction substantially transverse to said row and means responsive to deflection of said beam in said transverse direction for charging said deflector plate means to effect deflection of said beam in said parallel direction.

3. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, and means for selectively directing said beam to impinge upon one or another of said target electrodes, said directing means comprising a first pair of deflector plates effective when energized to deflect said beam in the direction of said row,- a second pair of deflector plates effective when energized to deflect said beam in a second direction at an angle to said first direction and means responsive to deflection of said beam in said second direction for establishing a potential difference between said first deflector plates.

4. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, av flrst deflecting means efiective when energized to deflect said beam in the direction along said row, and means for controlling said deflecting means to step said beam from one target electrode to another, said controlling means comprising an auxiliary electrode opposite said target electrodes, extending transversely with respect thereto and connected to said deflecting means to energize said deflecting means proportionately to the portion of the beam current to said auxiliary electrode at any time, a second deflecting means effective when energized to deflect said beam in a second direction at an angle to said first direction and means for supplying energizing pulses to said second defleeting means to deflect said beam out of impinging relation with said auxiliary electrode.

5. An electron discharge device comprising a said target electrodes,

plurality of target electrodes mounted in a row,,.

means for projecting an electron beam toward said target electrodes, a first deflecting means effective when energized to deflect said beam in the direction along said row, means for energizing said deflecting means to direct said beam nor mally upon a preassigned one of said target electrodes, a second deflecting means efiective when energized to deflect said beam in a second direction at an angle to said first direction, and

means for stepping said beam from said one target electrode in succession to a series of other target electrodes, said stepping means comprising means for applying energizing pulses to said second deflecting means and means responsive to deflection of said beam in said second direction for applying to said first deflecting means an energizing signal for each of said energizing pulses suflicient to step said beam from one of said target electrodes to a preassigned other target electrode.

6; An electron discharge device in accordance with claim 5 comprising means for automatically resetting said beam to impinge upon one of said target electrodes whenever it is stepped to a preassigned position.

7. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, a first deflecting means effective when energized to deflect said beam in the direction along said row, means for energizing said deflecting means to direct said beam normally upon one end target electrode, a second deflecting meansefiective when energized to deflect said beam transversely to said row, and means for stepping said beam in succession from said one end target electrode to the other end target electrode and then to the intermediate target electrodes, said stepping means comprising means for applying energizing pulses to said second deflecting means and means for converting deflection of "sami beam in response to said pulses into energizing signals applied to said first defleeting means.

8. An electron discharge device in accordance with claim '7 comprising means for automatically resetting said beam to impinge upon said other end target electrode when said beam is stepped to a preassigned other electrode.

9. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, 2. first deflecting means effective when energized to deflect said beam in the direction along said row, a second deflecting rneans effective when .energized to deflect said seem in a second direction at an angle to said first direction, and means for energizing said first ieflecting means to selectively step said beam from one target electrode to either the next pre- :eding or next succeeding target electrode, said I energizing means comprising means for applying energizing pulses of one polarity or the other to said second deflecting means and means for converting deflection of said beam in response to said energizing pulses mto signals applied to said first deflecting means and of effective polarity determined by the polarity of said pulses.

10. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward deflector plate means for the dimension parallel to said row, deflection means efiective when energized to deflect said beam transversely to said row, means for applying energizing pulses of one or the opposite polarity to said deflection means, and means for applying to said deflector plate means a charge variable in accordance with the polarity of said pulses to step said beam from one of said target electrodes to a preceding or succeeding target electrode in accordance with the polarity of said pulses.

11. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, deflecting means eflective when energized to deflect said beam in the direction transverse to said row, means for applying energizing pulses of one or the opposite polarity to said deflecting means, and means for stepping said beam from one target electrode to a preceding or succeeding target electrode in accordance with the polarity of said energizing pulses, said stepping means comprising a pair of deflector plates effective when energized to deflect deflecting said beam in said beam in the direction of said row and means responsive to deflection of said beam in said transverse direction for varying the potential between said plates in accordance with the polarity of said pulses.

12. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, a first deflecting means effective when energized to deflect said beam in the direction along said row, a second deflecting means efiective when energized to deflect said beam substantially normal to said direction, and an auxiliary electrode between said first means and said target electrodes and connected electrically to said first deflecting means, said auxiliary electrode having spaced oppositely extending fingers in interleaved relation and defining a plurality of windows one opposite each of said target electrodes and said fingers extending normal to said direction.

13. An electron discharge device comprising a plurality of target electrodes mounted in a row, means for projecting an electron beam toward said target electrodes, a first deflecting means efiective when energized to deflect said beam in the direction along said row, a second deflecting means effective when energized to deflect said beam in a second direction at an angle to said first direction, and an auxiliary electrode between said target electrodes and said first means and connected electrically to said first deflecting means, said auxiliary electrode comprising a plurality of spaced fingers extending parallel to said second direction and defining a plurality of openings one opposite each of said target electrodes.

14. An electron discharge device comprising an auxiliary electrode having therein a tortuous opening composed in part of substantially parallel portions, electron receiving means to one 11 side of said electrode and opposite said portions, means opposite the other side or said electrode for projecting an electron beam through said opening to said electron receiving means, a first deflecting means for deflecting said beam to sweep in one direction over said electrode across said parallel portions, said electrode being connected electrically to said deflecting means whereby said deflecting means is energized proportionately to the portion of said beam intercepted by said auxiliary electrode, and a second deflecting means for deflecting said beam in the direction parallel to said parallel portions.

15. An electron discharge device in accordance with claim 14 comprising a second auxiliary electrode adjacent one of said parallel portions and connected electrically to said second deflecting means.

16. An electron discharge device comprising electron receiving means, means for projecting an electron beam toward said electron receiving means, an auxiliary electrode between said first and second means and having parallel side portions and parallel fingers extending from each of said side portions, toward the other side portion and terminating short thereof, the fingers extending from the two side portions being in alternate relation, a first deflecting means for deflecting said beam in the direction parallel to said fingers, and a second deflecting means connected electrically to said auxiliary electrode to be energized in accordance with the beam current intercepted by said auxiliary electrode, said second deflecting means being positioned to deflect said means normal to said first direction.

17. An electron discharge device in accordance with claim 16 comprising a second auxiliary electrode connected to said first deflecting means and positioned adjacent one of said fingers.

18. An electron discharge device in accordance with claim 16 wherein said auxiliary electrode comprises portions adjacent one of said side portions, inclined with respect thereto and each extending between a corresponding pair or fingers extending from said one side portion.

19. An electron discharge device comprising electron receiving means, means for projecting an electron beam toward said electron receiving means, a pair of deflector plates positioned to deflect said beam in one direction, means for defleeting said beam in a second direction at an angle to said first direction, and means for placing a charge upon one of said plates in response to deflection of said beam by said deflecting means, said last means comprising an auxiliary electrode between said electron receiving and beam projecting means, connected to said one plate and having a pair of side portions extending in said one direction and fingers extending from each side portion in said second direction toward the other side portion and terminating short thereof, the fingers extending from the two side portions being arranged in alternate relation,

20. An electron discharge device comprising electron receiving means, means for projecting an electron beam toward said electron receiving means, a first pair of deflector plates between said electron receiving and beam projecting means and positioned to deflect said beam in one direction, a second pair of deflector plates between said electron receiving and beam projecting means and positioned to deflect said beam at substantially right angles to said first direction, and an auxiliary electrode between said electron receiving and beam projecting means and connected electrically to one of said first pair of deflector plates, said auxiliary electrode comprising parallel side members extending in said one direction and parallel fingers extending from each 01 said side members and normal to said one direction toward the other side member and terminating short thereof.

RAYMOND W. SEARS. 

